Camera mechanism



April 1945- s. B. GRIMSON 3 2,373,243 CAMERA MECHANISM Filed May 6, 19433 Sheets-Sheet 1 INVENTOR SHMUEL B. GRIMSON ATTORN EYS April 1 5. s. B.GRIMSON CAMERA MECHANISM Filed May 6, 1945 :5- Sheets-Sheet 2' INVENTORSHMUEL B. GRlMSON ATTORNEYS April 10, 1945. s. B. GRIMSCSN CAMERAMECHANISM.

Filed May 6, 1943 s Sheets-Sheet s INVENTOR SHMUEL B. GRMSQN v ATTORNEYSPatented Apr. 10, 1945 UNITED srs'ras rsrsur orrlcs CAMERA MECHANISMSamuel B. Crimson, New York, N. Y., assignor to Color ResearchCorporation, New York, N. Y.. a corporation of Delaware Application May6, 1943, Serial No. 485,809

' plate, from the front, in the region of the aper- Claims.

This invention relates to improvements in that part of a motion picturecamera comprising a pressure plate or the like for holding the film stationary and flat at the aperture of theapert-ure plate during exposure.

The main object of this invention is to provide an improved form ofpressure plate actuating mechanism for use in motion picture cameras andespecially motion picture cameras to be used in the makingof coloredmotion pictures.

A more specific objectof this invention is to provide a reciprocablepressure plate actuated by and in timed relation with the filmpull-downmechanism of a motion picture camera, whereby the film is clamped at theaperture, during exposure, so as to lie in an absolutely flat plane, foruse particularly in the taking of colored pictures, and morespecifically in taking colored pictures in a specializedprocess, whereextreme accuracy of register and flatness of the film durmg exposure isrequired. l

A still more specific object of the-invention is to provide an operatingmechanism and such a pressure plate as a part of the Mitchell camera,now extensively used in taking sound motion pictures. I

Another object of the invention is to provide a device of this typewhich is extremely quiet, indeed substantially noiseless in operation.

Other and more detailed objects of the invention will be apparent fromthe following description of the embodiment thereof illustrated in theattached drawings.

This invention resides substantia-1ly in the combination,construction,arrangement and relative location of parts, all as will bedescribed in detail below.

In the accompanying drawings,

Figure l is a side elevational View partly in vertical cross-section ofthe film pull-down mechanism of a Mitchell camera showing the pressureplate of this invention and its operating mechanism; illustrating itsactuation in proper timed relation with and by the pull-down mechanismFigure 2 is a View similar toFigure 1 showing the pressure platereleased as distinguished from Figure 1, in this respect, where thepressure plate is in applied position; v

Figure 3 is a cross-sectional view taken on the line 3-4 of Figure 1;

Figure 4 is a cross-sectional view taken on the, line 4-4 of Figure 1,showing the aperture symmetrically placed with respect to the runners;and

Figure 5 is a detail view showing the aperture ture.

The subject matter of this invention comprises a pressure plate and itsactuating mechanism, as described, for use with and as a part of aMitchell camera film pull-down or feeding device. The Mitchell mechanismas now used commercially and to which the subject matter of this invention is applied is disclosed in United States Patent No. 1,930,723issued October 17, 1933, to Martin A. Mitchell.

In the Mitchell camera, as now commonly employed, the pressure plate atthe film aperture consists essentially of a supporting plate positionedopposite the aperture on which is mounted a plurality of rollers whichextend transversely of the direction of movement of the film and are ofsufiicient length so as to clamp the perforated side edges of the filmagainst the surface of the aperture plate along which the film travels.In this camera the aperture plate on the film side above and below theaperture is relieved so that the film does not touch the aperture plateand is, therefore, not scratched as it moves. In other words, the filmmoves past the aperture in engagement with the adjacent face of theaperture plate along two raised bands at the sides of the aperture, butis out of contact with the aperture plate at all other portions. Theclamping rollers and their support do not move as the film is pulleddown, although, of course, the rollers are free to revolve as it moves,so that their contact with the film is a rolling contact. Thisarrangement is entirely satisfactory for the simultaneous recording ofpictures and sound because the mechanism is quiet, and forordinarypurposes, the roller pressure plate holds the film at theaperture in a sufficiently fiat condition. A further difficulty withthis and some other stationary pressure plate cameras is in the tendencyfor emulsion to pile on the surface of the runners, requiring frequentremoval and cleaning of the aperture plate.

However, for certain specialized methods of picture recording, andparticularly in the recording of color by some methods, it becomesnecessary to hold the film in as nearly a perfectly fiat plane as ispossible, and it has been found that the roller type of pressure plateis not suitable for the purpose, partly because the film is unsupportedat the top and bottom of the aperture,

as previously explained.

In accordance with this invention'the region of the aperture plate atthe top and bottom of the aperture, as well as at the sides, all lie ina single plane and the clamping plate engages the film throughout thearea of each frame, as it is exposed, and clamps the portion surroundingthe exposure area against the aperture plate onall sides of theaperture. With this arrangement, provision must be made for releasingthe pressure plate during the periods of movement of the film in orderthat the film will not be dragged across the clamping areas at the topand bottom of the aperture, thereby preventing scratching of the areasof each frame upon which the picture is to be exposed.

It follows, therefore, that the pressure plate must move rapidly intoand out of engagement with the film in synchronism with the operation ofthe pull-down mechanism, so that the pressure plate is released whilethe film is in motion and is in clamped position while the film is atrest. The subject matter of this invention is concerned with such amovable pressure plate and the operating mechanism therefor, designedfor incorporation in a Mitchell film feeding mecha nism for operationthereby.

An important object of the invention is to provide such a mechanismwhich will be silent. The mechanism herein disclosed is substantiallynoiseless and yet employs a reciprocating pressure plate of the typeindicated above. It is believed that this represents a distinct advancein the art in view of the fact that well known prior art cameras using areciprocating pressure plate lead to be abandoned when recording soundmotion pictures, and were in fact in a large measure displaced by theMitchell camera because of the excessive noise created bythem whenoperating.

In the drawings the film pull-down or feeding mechanism of the Mitchellcamera, as now used, is illustrated in cooperative relationship with thereciprocating pressure plate and the mechanism for operating it from thefilm feeding mechanism. As illustrated, the aperture plate 2, isattached to the supporting plate I by means of machine screws 3 and 4 sothat these two plates are held in a right angle relationship, as isclear for example from Figure 3. The aperture comprises the opening A atthe inner side of an outwardly opening enlarged recess provided as aseat for an element forming a part of a specialized mechanism andprocess which necessitated the development of the subject matter hereindisclosed. Attached to the outside of plate I, as appears from Figure 3,is a post or hub 5 in which is journaled a shaft 6, to which a helicalgear I is attached. Driving power for the mechanism is applied to shaft6 and other parts of the apparatus not here shown are driven b the gearI. all as is well known with devices of this type. The inner end ofshaft 6 appears-in Figure 1 and is enclosed by and journaled in aremovable cap 8. At the end of shaft 6 is an eccentric disc 9 on whichis mounted an oscillatory yoke In which is provided with a radiallyextending pin I I slidably engaging a guide block I2 mounted foroscillatory movement on the plate I by meansof a pivot pin I3.

Pivotally mounted on the yoke It) by means of a pivot screw i4 is an armI 5 which has an elongated slot extending therethrough within which itis slidably engaged by a block I 6 pivotally mounted on a pivot screw I8attached to the face of the eccentric disc 9 and eccentric with respectboth to the disc and the shaft 6. A bearing washer I! engages thefinished face of the yoke I5 and lies between it and the screw l8. Theleft hand end, Figure 1, of the arm or yoke I5 forms the film engagingclaw I9, which is so shaped that a pair of sprocket hole engagingfingers I9 are provided at each side of the film (see Figure 5). Thesefingers operate in vertical slots 2|] in a guide plate 2| which ismounted in back of the aperture plate A and spaced a short distancetherefrom to define a vertical channel through which the film may movefreely in a lengthwise direction. This plate, which in the regularMitchell mechanism supports the roller pressure plate, is integral witha right angle base plate 22 attached to the inner face of the plate I bymeans of screws 23 and 24 (see Figure 1). The guide plate 2| is providedwith an enlarged aperture in line with the aperture A of the apertureplate.

The eccentric yoke I0 is provided with a rearwardly extending tail pieceupon which the pivot screw 25 is mounted to provide a pivotal supportfor a short link 25 which is bifurcated to receive on the pivot screw 21theend of a short lever 28. The lever 28 is pivoted intermediate itsends on the pivot pin 29 which is mounted on a supporting plate 39detachably'secured to a lever 3|. This lever 3| is provided with alongitudinally movable button or finger piece 32 which is held by aspring, not shown, in the position shown in Figure 3, in which positiona pin engages the base plate I and holds the lever 3i in the positionshown in Figure I. mounted on a pivot pin 33 supported n the base plateI. As is well known with regard to this mechanism, the lever 3| isthrown from the position shown in Figure 1 towards the right against astop pin 34 for further withdrawing the pins 40 for convenience inthreading-up the camera.

The upper end of the lever 28 is pivotally connected by the pivot pin 35to a rod 36 which is slidably mounted at the right hand end in a bracket31, the base 38.0f which is attached by screws to. the base plate I. Theother end of the rod 36 is provided with a crossbar 39 which extendslaterally in both directions, as is clear from Figures 3 and 4, and tothe ends of which are attached the film registration pins 40. These rgistration pins operate through aligned apertures in the guide plate 2|and aperture plate 2. These apertures are positioned so that thesprocket perforations of the film may register therewith, as is wellknown in the art. The pins 40 are slidably mounted in a bracket 4|secured to the base plate I. Thus the shaft 36 is supported at both endsfor reciprocatory movement in a longitudinal direction.

The mechanism so far described comprises the Mitchell camera filmfeeding mechanism minus the roller pressure plate and by itselfconstitutes no part of this invention. The mechanism is well known andis in actual commercial use, and a detailed description of how itoperates does not therefore seem necessary. It should sufiice to statethat the claw l9 has a compound oscillatory and reciprocatory movementwhich causes it to The lever.3l is pivotally I as to accurately positionthe film in the aperture. In accordance with this invention it isdesired to provide a pressure plate which it will operate in conjunctionwith the mechanism previously described and will clampthe film about theentire periphery of the aperture during exposure while releasing thefilm during the period that it is being pulled down. The addedmechanism, comprising the subject matter of this invention, has beenshaded in Figure 1 to distinguish it from the parts previouslydescribed. It includes a plate 42 which overlies the plate 22 and isheld in position by the screws 24, 'so-that both of these plates areattached to the base plate I, by means of the screws 24,. is'supportedby the plate 42, is a double ended lever 44 having a forked lower end,engaging a roller on a pin 45 mounted on the bracket 45' clamped to theshaft 36. The upper end of the lever 44 is provided with a pin 41engaging the forked end of a lever 48 which is pivotally mountedintermediate its ends on a pivot pin 50 attached to the plate 42. v Thelever 48 is provided with an enlarged Opening 49 in which the pivot. pin43 lies. This opening is of such size and shape as to permit oscillationof the lever 48 on the ivot pin 50. The lower end of lever 48 isprovided with a lateral extension having a slot therein in which a screw52 engages. This screw is mounted upon a T-shaped arm 53, the shape ofwhich is clear from Figure 4. The arm 53 has attached to it near itsends a pair of rods 54 which are slidably mounted in a guide bar 56,attached by means of a bracket 55 to the plate 42. The pins 54 arefastened, to a plate 51 and support it {or reciprocation to and from theaperture plate, in the opening in the guide plate 2|. Mounted upon thesupporting plate 51 by means of four screws 59 is a perforated pressureplate 58. Between these two plates is a flat spring 60 (Figure 4) whichnormally tends to hold the plates in separated position, as clearlyshown in Figure 2.

The film which is shown at F engages the aperture plate in the region ofits sprocket perforations on guiding surfaces 5| (see Figure 3) whichextend vertically of the aperture plate and over which the filmslideswhen it moves. In accordance with this invention and asdistinguished from the arrangement when the roller type of pressureplate is used, the aperture plate is built up at the top and bottom ofthe aperture as shown at 62 and 63, Figure 1, so as to provide contactsurfaces in the plane of the guides 6| across the top and bottom or theaperture. The pressure plate 58 clamps the film not only at the sides ofa frame but at the top and bottom thereof This insures that the .filmwill be held at the Mounted on a pivot screw 43, which aperture in anabsolutely flat plane during exposuch relationship that the pins releasethe film at w the instant the claw starts the film in its downwardmovement and re-engages the film at the end of its movement. The claw [9has a combination oscillatory and rotational movement such that the clawfingers l9 move in a substantially horizontal direction from theposition shown'in Figure 1 into the position shown in Figure 2 beforethey begin their rotary movement which causes them to move downwardlywhile slowly retracting so as to define a path similar to that in have amovement quite similar to that of the registration pins and in about thesame timed relation. The pressure plate should be moved back to theposition shown in Figure 2 at the time the registration .pins 40 arewithdrawn and at which time the claw is moving the film. At the end ofthe film movement the pressure plate returns to the position shown inFigure 1' at the time the pins 40 are also moving to the position shownin the same figure. The pressure plate has a much smaller distance tomove than do' the registration pins, and indeed the total movement ofthe pressure plate is of the order of about fiiteen-thousandths of aninch. This movement issecured from the reciprocating rod 3Swhich'has agreat deal longer stroke. A double reduction movement is efiected bymeans of the plural lever arrangement illustrated so that while the rod3'6 is making its normal full stroke the pressure plate is moved therebythrough the reducing leverage system a distance no greater than aboutfifteenthousandths of an inch. The contact plate 58' of the pressuremechanism does not have as great a movement as does the backing orsupporting plate 5'! because of its sliding connection therewith on thepins 59. Thus as the backing plate 5! recedes during the first part ofthis stroke the actual pressure or contact plate 58 remains against thefilm but with a gradually reducing pressure as the tensed spring 60 isrelieved. When the supporting plate 57 engages the heads of the pins 59,as shown in Figure 2, the relative movement between the plates 5'! and58 is stopped and they move together. Thus the actual contact plate 58has a considerably less movement than does the backing plate 51. On thereturn stroke when the pressure is being applied to the film veryshortly after movement of the backing plate 5! begins the contactingplate 58 engages the film and from there on the further movement of thebacking plate 57 tenses the spring 60, increasing the pressure of theplate 58 on the film. This arrangement insures that no noise will begenerated by the mechanism even though it is operating, when in use, ata high rate of speed, as those skilled in the art will appreciate. Thecontact plate 58 is shown perforated so as to prevent a pumping actionor to prevent the trapping of any air behind the film.

As previously explained, the film when clamped lies between the contactplate 58 and the plateau comprising the sides 6!, the top 62 and thebottom 63 surrounding the aperture so that the film i clamped around theentire periphery of each frame during exposure against a very flatplate. Thus the film is for all intents and purposes in an. absolutelyfiat plane during exposure.

From the above description it will be apparent to those skilled in theart that the subject matter of this invention is capable of embodimentin physical forms other than that reproduced herein for illustrativepurposes. I do not, therefore, desire to be strictly limited to thedisclosure but rather by the claims granted me.

Whatis claimed is:

1. In combination with a Mitchell camera feed ing and registeringmechanism, the combination with an aperture plate, a film feedingdevice, longitudinally reciprocable registration pins and means foreffecting movement of the feeding mechanism and registering pins intimed relation, of a clamping plate for engaging the film throughout theperiphery of the aperture, means for supporting said clamping plateopposite the aperture in said aperture plate, lever meansinterconnecting said clamping plate with said mechanism, whereby theclamping plate is moved into and out of clamping engagement with theaperture plate in timed relation with said mechanism, said lever meanscomprising a lever pivotally mounted intermediate its ends and connectedat oneend to the registration pins, forming part of the registeringmechanism, a second lever pivotally mounted intermediate its ends andconnected at one end to said aperture plate, and means for connectingthe other ends of said levers together.

2. In a silent motion picture film feeding mechanism the combinationwith an aperture plate, longitudinally reciprocable registering pins, 9.pressure plate supported for reciprocatory parallel movement withrespect to said aperture plate, and means for reciprocating saidregistering pins of,'-a motion'reducing two-way positive driveconnection between said pin reciprocating means and said pressure plateto impart a timed movement to said pressure plate which is a frac-,

tion of the movement of said pins and of about the same duration.

3. In the combination of claim 2, said pressure plate including a;support, a, film engaging plate slidably mounted thereon, and resilientmeans interposed therebetween.

4; In the combination of claim 2, said Pressure plate including asupport, a film engaging plate slidably mounted thereon, and resilientmeans interposed therebetween, said aperture plate being undercut at theaperture to provide a film seat surrounding the aperture and lying in arelatively elevated single plane.

5. In the combination of claim 2, said motion reducing positive driveconnection comprising a lever pivotally mounted intermediate its endsand positively connected at one end to said pin reciprocating means, asecond lever pivotally mounted intermediate its ends and positivelyconnected atone end to said pressure plate, and means connecting theother ends of said levers together. I SAMUEL B. GRIMSON.

